Silicones are used in many products to enhance the products with the benefits of silicones. Such silicones which confer benefits to a composition may be called ‘active silicones’. For example, silicones (organopolysiloxanes) are used in many washing products to control foam formation. Silicones are also used in laundry products such as rinse cycle fabric softeners to give a soft feel to fabrics. Silicones are also present in many hair shampoos and other hair care products to enhance the shine and healthy appearance of the hair and are also present in skin care products such as shower gels to enhance the smooth feel of the skin.
Active silicones are often formulated as silicone oil-in-water emulsions comprising droplets of silicone oil dispersed in a continuous aqueous phase. Silicone oil-in-water emulsions require an additive to stabilize the emulsion, that is to prevent the droplets of silicone oil from coalescing into a continuous oil phase. The additives used are surfactants, that is amphiphilic molecules comprising a hydrophobic portion and a hydrophilic portion, as defined in Article 1, point 6 of the EC Directive No 648/2004 of 31 Mar. 2004. The surfactants are generally non-polymeric and may be anionic, cationic, nonionic or amphoteric. Examples of such surfactants suitable for silicon oil-in-water emulsions are given in many published patents, for example in WO-02/42360-A2.
However, surfactants are not acceptable in some applications, for example in certain food, personal care and cosmetics products where the formulation freedom and the choice of surfactants are severely restricted by legislation. Therefore there is a need to develop surfactant-free formulations and to develop stable silicone dispersions which can be mixed into food, personal care and cosmetics products more readily than pure silicones can be mixed.
U.S. Pat. No. 6,656,975 describes a silicone composition having a continuous phase of a polar organic liquid essentially requiring particles of a silicone active material encapsulated within an organic encapsulating material which is a solid at 25° C. Encapsulation is either via a layered core-shell structure of the emulsion or via matrix encapsulation. The silicone active material is sparingly soluble in the polar organic liquid at 25° C. but is substantially dissolved in the polar organic liquid at temperatures of from 40 to 100° C. The three phase contact angle between the organic encapsulating material, the silicone antifoam and the polar organic liquid is below 130°, with the angle measured through the silicone. The process described for making the composition necessitates a hot process in order to ensure that the silicone is encapsulated. However, this restricts the use of this product to silicones which are unaffected by heating. There must also be a surfactant present to ensure the silicone oil is fully encapsulated and furthermore a silicon based cross-linking material, typically a silicone resin as an essential ingredient which is not suitable for use in food related products. Hence, the products of U.S. Pat. No. 6,656,975 cannot be utilised in many food, personal care and cosmetics products.